The present invention relates to a differential pressure transducer. WO 8502 677-A discloses a differential pressure sensor in which two diaphragms are formed in a wafer. The diaphragms act against a fluid within a closed common cavity so that the deflections of the diaphragms are a measure of the difference between the pressures acting on the diaphragms. The deflections of the diaphragms are sensed by capacitive sensing.
U.S. Pat. No. 4,790,192 to Knecht issued Dec. 13, 1988 discloses forming a plurality of diaphragms side by side within a monolithic structure. Deflection of the diaphragms is monitored using strain gauges.
Electrical sensing techniques as employed in the above-described arrangements are susceptible to degradation through electrical noise and may not be suitable for use in hazardous environments. Additionally the direct measurement of the deflection of a diaphragm may not provide a high accuracy measurement with good resolution.
It has been found that highly accurate pressure measurements may be obtained by use of a vibrating beam mounted on a sensing diaphragm. However, due to the need to operate a vibrating beam in a substantially evacuated chamber, differential pressure sensing has not been possible with these existing sensors.